The art of animation is the rapid succession of a series of drawings, each showing a stage of movement slightly changed from the one before, to create the illusion of motion. Many methods for generating animated drawings and for producing animated sequences using computer hardware and software are known. Many of these methods have been considerably successful. Few of these methods, however, are capable of producing animated sequences in which the scenes comprising the sequences are fluid and precise, and which include even shading and blending of colors and textures.
The current practice of producing animation which utilizes paper, paint, ink, acetate or "cel" sheets, and film is a laborious task which has been illustrated in a series of U.S. patents dating back to the early 1900's. U.S. Pat. No. 1,107,193 (1914) to Bray, first introduced the notion of separating still or background elements from moving elements and figures. This permitted still elements to be drawn only once. U.S. Pat. No. 1,143,542 (1915) to Hurd, introduced a more practical method for doing this, and U.S. Pat. No. 1,715,127 (1929), taught an improved method of registering sheets of cel material.
Traditionally, animation is created using hand drawings and photographic equipment to record the hand drawings in a sequence to depict motion. This procedure first involves pose planning by an artist who then proceeds to draw a series of rough position poses on paper. Next, several key frames of a character are drawn on paper sheets or boards. The key frames, generally a source key and a target key, are intended to indicate the extremes of a range of motion the character is to undergo, or a distance to be traveled, and are generally designated as the main or key positions of the character. Next, these two key frames are placed on a translucent surface with a light or lightboard disposed underneath the translucent surface. An artist, generally referred to in the art field as an in-betweener, arranges the two key frames on the translucent surface so that the lines of both cels are clearly visible. An additional cel is then superimposed over the first two key frames. While viewing the underlying lines of the key frames, the in-betweener traces between the lines of the two key frames to produce an "in-between" frame having lines between the original lines of the key frames. Using the newly drawn in-between frame and the target frame, the process of producing another in-between frame is continuously repeated using the newly created in-between frame and the target key until the required number of frames are reached such that several in-between cels have been produced. The difference between the in-between drawings must be comparatively slight, consistent and of the proper character. When skillfully done, the object in the in-between drawings will appear to move smoothly and naturally when the pictures are displayed rapidly in sequence. Up to this point, the animator is dealing only with outlines having no color or shading.
After all the in-between frames have been produced, all of the frames are checked for smoothness, correctness, and continuity in the animations. A crude, but quick method of checking for continuity is to stack the cels upon each other in sequence and examine them in order by "rolling" them. "Rolling" is performed by firmly holding one edge of the stack of cels and slightly bending the other edge releasing the pages one-by-one in rapid succession. Alternatively, the cels may be viewed by scanning or digitizing the paper cels into a computer system and projecting the cels on the computer monitor at their appropriate rate of 24 or 30 frames per second, depending upon the medium to which they are to be ultimately stored upon. Using either of these methods, corrections are easily made by revising the in-between or creating substitute cels. Since the drawings cannot yet be seen in animation at true speed, oftentimes a "pencil test" is performed. A pencil test involves photographing or videotaping the rough drawings frame by frame, onto film or video tape. After developing the film or tape, the animator is able to judge the drawings and make any required correction. The pencil test is, however, extremely time consuming and often requires additional expensive equipment. As such, the test is done infrequently and often skipped altogether.
When all the drawing are complete, the paper cels are then traced or photocopied on to clear plastic acetate cel, or scanned onto a computer if electronic inking and painting is going to be used. If coloring is performed by hand, each cel is then carefully inked and painted on the reverse side. During painting, the colorist must be extremely careful not to paint outside the lines or to blend any colors. Oftentimes several layers of cels are used in complex animations, and different parts of the animation are painted onto separate cels. Cel paint must, therefore, be mixed to slightly different shades so that colors appear to match when covered with a differing number of layers of cel material. Cel paint must also be carefully matched from batch to batch. Moreover, once painted and cleaned, cels must be reordered and carefully checked prior to photographing. The cost of paints, inks and the skill and time required to paint each of the cels render this step in the animation process extremely expensive. Furthermore, since there are likely to be numerous cels which have all been excessively handled up to this point in the animation process, dust, fingerprints, and smudges may be a major problem. The cells thus require a careful cleaning after painting has been completed.
After all the cels have been painted, checked for accuracy and cleaned, they are photographed one by one and composited or overlaid on a background. This process is extremely tedious and time consuming. Furthermore, it is essential that the color sections be prevented from blending, since it would be impossible to retain a consistency of texturing, shading, and/or blending throughout the multiple cels.
For many years, the application of computers to animation has been part of an attempt to save the animator from making all of the in-between drawings, generating them instead by computational means rather than manually. In most instances, however, the artists skill in drafting the key frames is preferred over computer generated drawings which may often be crude and lack certain texture or "feeling." Computer technology has also introduced numerous software programs for adding special effects to the traditional animation process. In order to provide a desired texture to a character or object, some software programs require the animator to scan into the computer a small photograph of the texture which is desired. Thereafter, every time the animator desires that texture, it must be retrieved from the computer's memory and repeated or "layered" over the character or object until the desire texture is attained. In addition to producing less than acceptable texturing, this procedure is extremely burdensome and time consuming.
In addition to the traditional prior art method of animation, numerous other animation processes have been disclosed, both manual, computer generated and a combination of the two, along with numerous alternative methods for performing individual stages of the traditional animation process as disclosed. For instance, U.S. Pat. No. 4,9452,051 to Lovell et al. describes a method and system for drawing and manipulating cels via computer interface. The process recited for creating frames is similar to the traditional manner yet performed by a computer instead of by hand. The computer creates the bounding lines or character keys of the desired image and permits the animator to create in-between frames via computer computations of any two drawn key frames. Cel position may then be manipulated and color may be added using the computer. However, the resulting animation sequence generated by this process is less than desirable.
Accordingly, there is a need for a simple and time saving animation process which provides animated sequences in which non-segregated colors and shading, full texture, and fluid and concise movements are maintained over the entire animation.